The present invention relates to an ink-jet printer in which an array of ink-particles is generated from a pressurized ink by a nozzle tube to move toward a work piece, is charged with electricity by energized electrodes and is deflected by an electrically controllably energized deflecting plate so that each of the ink-particles injected from the ink-jet printer reaches a desirable position on the work piece to be printed.
A basic structure of the ink-jet printer as above mentioned is disclosed by, for example, U.S. Pat. No. 4,083,053.
As shown in FIG. 4, a conventional ink-jet printer has a suction pump 7 so that a part of the array of ink-particles which is not used to print the work piece and an air in a gutter 6 for receiving the part of the array of ink particles are taken into an ink-tank 1 from a printing head 9. The part of the array of ink-particles which is not used to print the work piece is contained again in the ink-tank 1, but, the air taken from the gutter into the ink-tank 1 is discharged from the ink-tank 1 to the atmosphere through a filter 16 in which an organic solvent contained by and generated from the ink is absorbed by an activated charcoal or the like. The ink is supplied to a nozzle tube 5 from the ink-tank 1 by an ink-pump 2 through an ink-pressure regulator 4. An air compressor 15 supplies a pressurized air into the printing head 9 from the atmosphere to prevent a penetration of undesirable substance into the printing head 9.